Babak ZIAIE, et al.
[ See also : KIM /
Electroactive paper ]
January 5, 2010
'Ferropaper' is new technology for small motors,
Researchers at Purdue University have created a magnetic
"ferropaper" that might be used to make low-cost "micromotors" for
surgical instruments, tiny tweezers to study cells and miniature
The material is made by impregnating ordinary paper - even
newsprint - with a mixture of mineral oil and "magnetic
nanoparticles" of iron oxide. The nanoparticle-laden paper can
then be moved using a magnetic field.
"Paper is a porous matrix, so you can load a lot of this material
into it," said Babak Ziaie, a professor of electrical and computer
engineering and biomedical engineering.
The new technique represents a low-cost way to make small stereo
speakers, miniature robots or motors for a variety of potential
applications, including tweezers to manipulate cells and flexible
fingers for minimally invasive surgery.
"Because paper is very soft it won't damage cells or tissue,"
Ziaie said. "It is very inexpensive to make. You put a droplet on
a piece of paper, and that is your actuator, or motor."
Once saturated with this "ferrofluid" mixture, the paper is coated
with a biocompatible plastic film, which makes it water resistant,
prevents the fluid from evaporating and improves mechanical
properties such as strength, stiffness and elasticity.
Findings will be detailed in a research paper being presented
during the 23rd IEEE International Conference on Micro Electro
Mechanical Systems on Jan. 24-28 in Hong Kong. The paper was
written by Ziaie, electrical engineering doctoral student Pinghung
Wei and physics doctoral student Zhenwen Ding.
Because the technique is inexpensive and doesn't require
specialized laboratory facilities, it could be used in community
colleges and high schools to teach about micro robots and other
engineering and scientific principles, Ziaie said.
The magnetic particles, which are commercially available, have a
diameter of about 10 nanometers, or billionths of a meter, which
is roughly 1/10,000th the width of a human hair. Ferro is short
for ferrous, or related to iron.
"You wouldn't have to use nanoparticles, but they are easier and
cheaper to manufacture than larger-size particles," Ziaie said.
"They are commercially available at very low cost."
The researchers used an instrument called a field-emission
scanning electron microscope to study how well the nanoparticle
mixture impregnates certain types of paper.
"All types of paper can be used, but newspaper and soft tissue
paper are especially suitable because they have good porosity,"
The researchers fashioned the material into a small cantilever, a
structure resembling a diving board that can be moved or caused to
vibrate by applying a magnetic field.
"Cantilever actuators are very common, but usually they are made
from silicon, which is expensive and requires special cleanroom
facilities to manufacture," Ziaie said. "So using the ferropaper
could be a very inexpensive, simple alternative. This is like 100
times cheaper than the silicon devices now available."
The researchers also have experimented with other shapes and
structures resembling Origami to study more complicated movements.
The research is based at the Birck Nanotechnology Center in
Purdue's Discovery Park.
Zhenwen Ding, Pinghung Wei, and
In this paper, we report on an inexpensive method for fabricating
mm-scale magnetic actuators using ferrofluid impregnated paper.
Different types of papers were loaded with light oil-based
ferrofluid, cut to cantilever shape, coated with parylene C, and
tested with an external magnetic field. Cleanroom and filter paper
were able to generate large forces (>40 mg equivalent force)
whereas soft tissue paper provided the largest deflection (40° tip
angle). Coating parylene on ferro-paper not only improves the
mechanical properties but also allows the ferro-paper actuator to
work in liquid environment.
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